I plan to determine the physiological function of rat liver alkaline phosphatase by: 1) attempting to identify a specific inducer of alkaline phosphatase, 2) by identifying physiological substances which serve as substrates for rat liver alkaline phosphatase and whose intrahepatic concentration may be regulated by the phosphohydrolase activity of alkaline phosphatase, and 3) by inhibiting alkaline phosphatase activity in vivo with either site-specific reagents or monospecific antibody to alkaline phosphatase and observing changes in either the composition and concentration of intrahepatic phosphoesters or the composition and concentration of bile products. I plan to use isolated, perfused rat liver, organ culture and incubation of isolated hepatocytes in the above experiments. I propose to study the catabolism of alkaline phosphatase, identify the site or sites at which catabolism occurs and isolate cell free systems capable of hydrolyzing alkaline phosphatase. I hope to develop affinity columns that will facilitate the purification of alkaline phosphatase. I plan to purify to homogeneity human liver, bone, kidney and intestinal alkaline phosphatase and study their protein structure. I propose to prepare specific antibodies to each of these enzymes and to develop radioimmunoassays to facilitate the measurement of each isoenzyme in human serum. Finally, I plan to study the mechanism of the elevated serum alkaline phosphatase in humans with liver disease to determine if it is the same as that which I have demonstrated in rats.